The present invention relates to a cross-coil rotary magnet device, particularly a device for setting a resettable mechanical counter, in particular a roller-type counter for measurement of distance travelled, having a stepping motor which is developed as two-phase stepping motor with a rotor which consists, in particular, of a permanent magnet with diametrically opposite permanent magnet poles, and having a coil arrangement with coils arranged at an angular distance apart of, in particular, 90.degree., and which is connected to the counter via a gearing.
One known cross-coil rotary magnet device is developed especially as a motor for driving a clockwork (Federal Republic of Germany OS No. 34 19 100). In that motor a rotatably mounted rotor has diametrically opposite permanent magnet poles. A multi-phase coil arrangement serves to produce a magnetic field which deflects the rotor as a function of control signals which are applied to coils of the coil arrangement. For this purpose the coil arrangement has several coils which surround the rotor, are arranged at equal angular distances apart and can be controlled by sinusoidal voltages staggered by a given phase shift. The coil arrangement consists, in particular, of two coils arranged at right angles to each other, and which are fed with two sinusoidal voltages which are 90.degree. apart. The axis of rotation or shaft can be the seconds arbor or minutes arbor of the clockwork. In the last-mentioned case, a minute hand is attached to one end of the rotary shaft and can be moved over a dial. An hour wheel which has an hour tube surrounding the rotary shaft, is driven by a drive pinion arranged on the rotary shaft and a minute wheel.
The foregoing motor, which is developed for driving a clockwork and is provided with drive pinion, minute wheel and hour wheel as well as an hour tube, is not intended for setting a resettable mechanical counter. Nor is it amenable to construct for this purpose a compact structural unit, in particular with a roller type counter. There is furthermore lacking a resetting device for the counter.
In a device of the state of the art for the indicating of a mechanical variable, in particular the speed of a motor vehicle, a measuring mechanism is provided for setting a pointer, the measuring mechanism being connected via a converter to a transmitter which produces a pulse having a pulse frequency which is proportional to the measurement variable (Federal Republic of Germany OS No. 27 30 699). A stepping motor which travels forward and backward serves as measuring mechanism. The stepping motor is fed with a sign-valued pulse train which is produced from counting values which are formed during successive defined time intervals as a function of the measurement variable and which, when compared to each other, result in a sign-valued difference value. The stepping motor which sets itself corresponding to this difference value is coupled to an indicator mechanism via a gearing. The foregoing stepping motor, however, is not readily suitable for the setting of a resettable mechanical counter, in particular a roller type counter for measurement of distance travelled, since a resetting by the driving pinion of the stepping motor, if it would work at all, would at least take too long as far as the rollers for the higher numerical positions are concerned.
Odometers or other roller type counters are customarily driven by a stepping motor which rotates only in one direction. The resetting of the counter takes place either manually, by a stroke magnet or an additional motor. The resetting takes place in this connection via a so-called zero setting shaft which, in its turn, can reset the individual rollers of a roller-type counter via heart cams by a brief turn of at most 180.degree.. A separate drive with resetting mechanism is required for this type of resetting.